The use of finger joints in timber joints is common. However, some problems are connected to these joints.
One problem is that the fingers remain visible on all sides, but usually they are visible at least on two sides. The visible fingers cause many kinds of problems. They are an esthetical disturbance. Usually they cannot be painted without rough working as grinding and filling. From visible fingers water and dirt can harmfully penetrate into the wood.
Another disadvantage connected to finger joints is that the finger grooves reach outside the joint. Such a finger joint solution is presented among others in publication U.S. Pat. No. 3,452,502. From connection pieces material is removed outside the joint area, which reduces the firmness. The fingers outside the joint are aesthetically bad and in addition water and dirt can harmfully gather in them. Also such a problem is connected to the finger joints that by assembly the joints are difficult to locate. Finger cuttings do not locate the connection pieces accurately in regard to each other.
Present finger joints are not in an optimal way firm, since they have structural discontinuities, which cause great local tensions.